When a motion picture having moving objects is shown on a liquid crystal display, human eyes may perceive the edges of the objects as blurred due to persistence of vision and slow response time of the display. For example, referring to FIG. 1A, an LCD 100 shows a black object 106 that moves from a first position 102 at time t1 to a second position 104 at time t2 against a white background (the left portion of the object 106 is outside of the display area at time t2). Assuming that the difference between t1 and t2 is short, the human eye at time t2 may perceive an image shown in FIG. 1B, in which the boundary between the black object 106 and the white background (108) is blurred.
Referring to FIG. 1C, a graph 110 showing a motion picture response curve (MPRC) 112 can be used to evaluate the blurriness effect. The MPRC 112 is a brightness distribution curve and represents the perception of an edge of a moving object by human eyes. A steep motion picture response curve indicates that the edges of the motion picture are clear, whereas a gradually sloped motion picture response curve indicates that the edges of the motion picture may be blurred. A blur edge width (BEW) parameter is defined as the number of pixels between a location 114 having 10% full luminance and a location 116 having 90% full luminance near the edge of the object being examined. A narrower blur edge width indicates that the edge of the object is better defined, whereas a wider blur edge width indicates that the edge of the object is less well defined and may be blurred.
The quality of displayed motion pictures can be expressed by BEW normalized by the motion speed of the moving object expressed in pixels per frame:N-BEW (frame)=blur edge width (pixel)/moving speed V (pixel/frame).  (Equ. 1)The N-BEW value can be calculated for a number of gray levels, and their values are averaged. A motion picture response time (MPRT) parameter can be derived by multiplying the averaged N-BEW values by the frame time Tf of the liquid crystal display:MPRT (seconds)=N-BEW (averaged over gray levels)×frame time Tf (seconds/frame).  (Equ. 2)A smaller motion picture response time indicates a better motion picture quality, whereas a larger motion picture response time indicates a poorer motion picture quality.